The invention relates to a method for the preparation of relief structures by phototechniques from mixtures containing acrylate- and/or methacrylate-group-containing polymers and photo-initiators.
One of the most accurate structuring methods for insulating materials, semiconductor and conductor materials in electrical engineering is the phototechnique. In this process resist relief structures generated by phototechniques are copied onto substrates by suitable methods such as etching, vapor deposition and electroless or electrodeposition plating. Resist relief structures can furthermore also perform a permanent protection function, for example, as insulating material.
In a method known from U.S. Pat. No. 3,957,512 and U.S. Pat. Re. 30,186, both incorporated herein by reference, relief structures are made from highly heat-resistant polymers. For this purpose, radiation-sensitive soluble preliminary polymer stages are applied to a substrate in the form of a layer or a film; the radiation-sensitive layer or foil is then exposed through negative patterns; and subsequently, the non-irradiated layers or film portions are removed from the substrate. If necessary, this can be followed by tempering the relief structure obtained. Soluble preliminary polymer stages used with this method are polyaddition or polycondensation products of polyfunctional carbocyclic or heterocyclic compounds containing radiation-sensitive radicals, with diamines, diisocyanates, bis-acid chlorides or dicarboxylic acids. The compounds carrying the radiation-sensitive radicals contain two carboxyl, carboxylic acid chloride, amino, isocyanate or hydroxyl groups suitable for addition or condensation reactions and partially, in ortho or peri-position thereto, radiation-reactive groups bound to carboxyl groups as esters. According to U.S. Pat. No. Re. 30,186, these radiation-reactive groups are oxyalkylene-acrylate or oxyalkylene-methacrylate groups.
The light sensitivity of resist materials such as photo-reactive polymers can be increased through addition of photo-initiators and photo-sensitizers. This is important because the economics of structuring of surfaces by phototechniques dictate that the time for which the expensive exposure equipment is used be as short as possible, i.e., the highest possible sensitivity of the photoresist is required. In the known method, compounds such as Michler's ketone, i.e., 4,4'-bis(dimethylamino)-benzophenone, benzoin ether, 2-tert-butyl-9,10-anthraquinone, 1,2-benz-9,10-anthraquinone and bis(diethylamino)-benzophenone are added to the preliminary polymer stages for this purpose. To increase the light sensitivity, copolymerizable radiation-sensitive maleinimides also can be added to the preliminary polymer stages.